Test if std::vector<> contains a specific entry

[SteveS]

How do I test to see whether or not a vector contains a specific entry? I've looked all over the MSDN doc on std::vector and I don't see anything.

For example:

std::vector<int> myVector;
myVector.push_back(10);
myVector.push_back(20);
myVector.push_back(30);

Aside from looping through the vector manually, what do I do to determine if the vector contains the value 20?

Thanks

[Paul McKenzie]

Originally posted by SteveS
How do I test to see whether or not a vector contains a specific entry? I've looked all over the MSDN doc on std::vector and I don't see anything.

That is because what you are looking for is an STL algorithm that works for many different containers, not just vector.

Use the std::find() algorithm. Note that std::find also works on plain old arrays too.

#include <vector>
#include <iostream>
#include <algorithm>

int main()
{
    std::vector<int> myVector;
    myVector.push_back(10);
    myVector.push_back(20);
    myVector.push_back(30);
   
    std::vector<int>::iterator it = std::find( myVector.begin(), myVector.end(), 20 );
    if ( it != myVector.end() )
    {
          std::cout << "Found the element at position " <<
                    std::distance( myVector.begin(), it ) << std::endl;

          std::cout << *it;
     }
}

Regards,

Paul McKenzie

[SteveS]

Beautiful!

Works perfectly! Thanks a lot!
I have a list of C++ related books that I'm working through and STL is one of them. I think I'll put that one higher in the priority!

Thanks

[Sam Hobbs]

Note that if the data is sorted it can be searched more efficiently. For small amounts of data it is efficient to search sequentially but for a large amount of data it could be quite significantly better if the search is not sequential.

[Paul McKenzie]

To add to Sam's post, if your data is sorted, you can use the binary_search() algorithm function.

Regards,

Paul McKenzie